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Simulating Future GPS Clock Scenarios with Two Composite Clock AlgorithmsUsing the GPS Toolkit, the GPS constellation is simulated using 31 satellites (SV) and a ground network of 17 monitor stations (MS). At every 15-minutes measurement epoch, the monitor stations measure the time signals of all satellites above a parameterized elevation angle. Once a day, the satellite clock estimates the station and satellite clocks. The first composite clock (B) is based on the Brown algorithm, and is now used by GPS. The second one (G) is based on the Greenhall algorithm. The composite clock of G and B performance are investigated using three ground-clock models. Model C simulates the current GPS configuration, in which all stations are equipped with cesium clocks, except for masers at USNO and Alternate Master Clock (AMC) sites. Model M is an improved situation in which every station is equipped with active hydrogen masers. Finally, Models F and O are future scenarios in which the USNO and AMC stations are equipped with fountain clocks instead of masers. Model F is a rubidium fountain, while Model O is more precise but futuristic Optical Fountain. Each model is evaluated using three performance metrics. The timing-related user range error having all satellites available is the first performance index (PI1). The second performance index (PI2) relates to the stability of the broadcast GPS system time itself. The third performance index (PI3) evaluates the stability of the time scales computed by the two composite clocks. A distinction is made between the "Signal-in-Space" accuracy and that available through a GNSS receiver.
Document ID
20150006900
Acquisition Source
Jet Propulsion Laboratory
Document Type
Conference Paper
External Source(s)
Authors
Suess, Matthias
(Deutsches Zentrum fuer Luft- und Raumfahrt e.V. Oberpfaffenhofen, Germany)
Matsakis, Demetrios
(Naval Observatory Washington, DC, United States)
Greenhall, Charles A.
(Jet Propulsion Lab., California Inst. of Tech. Pasadena, CA, United States)
Date Acquired
April 29, 2015
Publication Date
November 16, 2010
Subject Category
Electronics And Electrical Engineering
Numerical Analysis
Space Communications, Spacecraft Communications, Command And Tracking
Statistics And Probability
Meeting Information
Meeting: Annual Precise Time and Time Interval Systems and Applications Meeting (PTTI 2010)
Location: Reston, VA
Country: United States
Start Date: November 15, 2010
End Date: November 18, 2010
Sponsors: Institute of Navigation
Distribution Limits
Public
Copyright
Other
Keywords
global positioning system
Kalman filter
timescale

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